Fast-forward 15 years, and Apple has risen from the ashes to become the hottest company on Earth—a corporate behemoth that, for a time earlier this year, boasted the highest market capitalization in history, a claim Microsoft once could make.

Microsoft, meanwhile, has slipped from its perch on top of the corporate world and while it is still a business giant nowhere near a bankruptcy filing, the business shift from desktops and laptops to mobile devices and the cloud has put Microsoft in the unfamiliar position of playing from behind.

That’s a big part of what makes the recent launch of Windows 8 the most important product release from Microsoft in a couple of decades. Windows 8—and the concurrent debuts of the Windows Phone 8, the Microsoft Surface tablet and the Windows RT mobile operating system—represents the most significant surge in Microsoft’s big push to make itself a major player in the mobile and cloud markets.

What does all of this have to do with CPAs? Microsoft’s mobile and cloud fate will affect virtually every accountant. Windows has long been the dominant operating system used by accountants (and pretty much everyone else), and Excel has long been one of the most important, if not the most important, software application used in the profession.

With Windows 8, Microsoft is hoping to leverage its dominance among businesses and other commercial users to climb into a competitive position with Apple and Google, the leading makers of operating systems for smartphones and tablets. By establishing a consistent user interface and experience on smartphones, tablets, laptops, desktops, Ultrabooks and laptop-desktop convertible devices, Microsoft is seeking to lure established business customers who have been unsure exactly how to adjust to and adopt mobile devices. The thinking here is simple: Customers comfortable with using Windows are more likely to embrace mobile devices that run on Windows.

Time will tell if that strategy works. In the meantime, CPAs running Windows 7, Vista or XP must decide whether and when to upgrade to Windows 8. In addition, CPAs need to educate themselves on the various mobile devices and cloud computing options. The days of working solely on a desktop PC and/or laptop are over, just as surely as the era of logging into mainframe computers is part of the past. CPAs, charged with making sense of a complex and changing world, must make sense of the complex and changing landscape of information technology.

For more on Windows 8 and the impact of mobile computing, check out the November Journal of Accountancy article “Windows 8: Jump or wait?” CPAs interested in a deeper dive into the subject, and a chance to earn a CPE credit, can sign up for the JofA webinar series webcast, Windows 8: What CPAs Need to Know, which will take place 3 to 4 p.m. ET on Dec. 5.